In hybrid electric and battery electric vehicles, a high-voltage DC battery pack provides some of the power necessary for propelling the vehicle. The battery pack energizes an inverter module over a high-voltage DC bus. The inverter module converts the DC voltage from the battery pack into an AC waveform, and thereafter energizes one or more motor/generator units over a high-voltage AC bus with the AC waveform. Torque from the motor/generator unit(s) may be used thereafter to provide input torque to a transmission or to generate electricity for recharging the battery pack.
The battery pack can be electrically isolated from the vehicle chassis and electrical components of the vehicle powertrain in part by selectively opening solid-state contactors under certain operating conditions, for instance upon vehicle shutdown or in the presence of a detected electrical fault. The conductive leads of one or more of the contactors can become stuck or welded closed. However, voltage sensors used for detecting a welded contactor condition can fail, thereby complicating the diagnosis and isolation of welded contactor and stuck-in-range voltage sensor faults.